The present invention relates to a thin film of a polymer and a device having the thin film, and more particularly to a thin film formed from a modified polymer by the Langmuir-Blodgett technique and a device having the thin film.
In the 1930s, it was found by Langmuir and Blodgett that a fatty acid having 16 to 22 carbon atoms could form a monolayer (monomolecular film) on the surface of water and the monolayers could be built up on a substance to form a multilayer film. In recent years, various studies have been made on the applications of the built-up films, namely Langmuir-Blodgett films (hereinafter referred to as "LB film"). Various studies made already are disclosed in, for instance, Kotaibutsuri 17, No. 12, 45(1982), Thin Solid Films, 68, No. 1 (1980), Thin Solid Films, 99, No. 1.2.3 (1983), Insoluble monolayers at liquid-gas interfaces (G. L. Gains, Interscience Publishers, New York, 1966), and the like.
The LB films of the straight-chain saturated fatty acids are poor in heat resistance and mechanical strength and are not suitable for practical uses. In order to address the above problem, there are proposed, for instance, polymerizing films formed from unsaturated fatty acids such as .omega.-tricosenoic acid, .omega.-heptadecenoic acid and .alpha.-octadecylacrylic acid, unsaturated fatty acid esters such as vinyl stearate and octadecyl acrylate, or diacetylene derivatives. However, these films are insufficient in heat resistance, electric property and other properties. It is also known that some hydrophilic group-containing polymers, such as polyacrylic acids, polyvinyl alcohols, polyethyl acrylates and polypeptides, also have film-forming properties. However, none of them are suited as a material for LB films, and no investigations have been made on modification of polymers to be used, in particular, as a material for LB films. Also, composite articles having the above-mentioned film are poor in heat resistance and mechanical strength, and are not suitable for practical use.
On the other hand, it is well known that films of polyimide have excellent heat resistance. The thickness of the films prepared, for instance, by spin coating is at least 1,000 .ANG., usually 1 .mu.m or more. It is very difficult to form a heat resistance polyimide film with a thickness of less than 1,000 .ANG. and with no pin-hole, and it is impossible to prepare devices having such thin polyimide films.
It is an object of the present invention to provide a polymer thin film having improved heat resistance, chemical resistance and mechanical properties such as adhesion, and having a thickness hardly attainable by conventional process.
A further object of the present invention is to provide a device having the above polymer thin film.
These and other objects of the present invention will become apparent from the description hereafter.